1. Field of the Invention
The present invention relates to a cruise control apparatus having a function to cause an own vehicle (a vehicle equipped with this cruise control apparatus) to run following a preceding vehicle.
2. Description of Related Art
There is known a vehicle-mounted radar apparatus configured to transmit a radar wave (a laser wave or a millimeter wave, for example) and detect an object present around the vehicle based on a reflected version of the radar wave.
Such a vehicle-mounted radar apparatus is used for the so-called auto cruise control which operates to detect a preceding vehicle (a vehicle running ahead in the same lane as the own vehicle), and cause the own vehicle to run keeping constant the following distance to the preceding vehicle.
There is known a technique in which a front vehicle (a vehicle running ahead of an own vehicle) is recognized as a preceding vehicle the following distance to which the own vehicle should keep constant, in accordance with probability that the front vehicle is running in the same lane as the own vehicle (may be referred to as “the own vehicle lane” hereinafter), the probability being calculated based on the curve radius of the lane in which the own vehicle is running and the relative position of the front vehicle. This technique is for preventing a vehicle running under control of the auto cruise control from erroneously recognizing a front vehicle running in a lane different from the own vehicle lane as a preceding vehicle. For example, refer to Japanese Patent Application Laid-open No. H8-279099.
However, the above conventional technique has a problem in that the accuracy of detection of the position of a front vehicle is reduced while the front vehicle makes a turn, because the lateral position (the position in the width direction of the own vehicle) of a point of the front vehicle at which the radar wave reflects (referred to as “the front vehicle reflection point” hereinafter) shifts in the direction of the turn (that is, shifts leftward while the front vehicle makes a left turn, and shifts rightward while the front vehicle makes a right turn). This is because the own vehicle receives the radar wave reflected mainly at the center portion of the back side of the front vehicle when the front vehicle is running straight, receives the radar wave reflected mainly at the left end portion of the back side of the front vehicle when the front vehicle is making a left turn, and receives the radar wave reflected mainly at the right end portion of the back side of the front vehicle when the front vehicle is making a right turn.
Particularly, when the front vehicle is a large size vehicle such as a truck, since the distance between the center portion and the left or right end portion is large, reduction of the accuracy of detection of the position of the front vehicle increases.